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RE: JJ 300B - loose bases - inverted operation

Michael, hi. The JJ 300B's ceramic bases are fastened to the bottle with what appears to be RTV - silicone rubber. I would have thought this would have been sufficient to hold the it while the amp was inverted. Mind you, I have not done surgery on one - just observed and felt how secure the bottle is in the base. RTV on curing imposes an elastic bed between glass and ceramic and serves to cradle the bottle. Are you sure there weren't other forces that may have acted on the tubes? It is easy for these things to happen. Remember the base is made to grip and torque not the bottle. Lots of tubes damaged this way. The ceramic base JJ chose has great eye appeal - white porcelain, fired on logo, gold flashed pins. Measurement will show the OD is about 1mm larger than normal. It doesn't have the usual phenolic-like compound used to bond most bottles into their sockets. The usual quick fix (clear nail polish or crazy glue) won't find an inner surface with which to bond. I would investigate: is the bottle separated from the RTV or is the RTV loose from the ceramic base? It should be simple to re-attach in either case.


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